Fluid turbine systems

ABSTRACT

Various fluid turbine systems and methods are described. The turbine can be a vertical axis wind turbine configured to generate power from wind energy. The turbine system can have a blade assembly. The blade assembly can have a plurality of blades rotatable about an axis. The turbine system can have a concentrator positionable upwind and in front of a return side of the blade assembly. The concentrator can define a convex surface facing the wind. The turbine system can also have a variable concentrator positionable upwind of a push side of the blade assembly. The variable concentrator can be adjustable between a first position and a second position, the variable concentrator being capable of deflecting more wind toward the turbine in the first position than in the second position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to and claims the benefit of U.S.Provisional Application No. 61/094,386, filed Sep. 4, 2008, the entiredisclosure of which is hereby incorporated by reference herein.

BACKGROUND OF THE INVENTIONS

1. Field of the Invention

This application relates to fluid turbines, and more particularlyrelates to vertical axis fluid turbines.

2. Description of the Related Art

Turbines have been used to generate power from moving fluids, such aswater or air. However, known units and various components thereof havevarious well known limitations and disadvantages.

SUMMARY OF THE INVENTIONS

Example embodiments described herein have several features, no singleone of which is indispensable or solely responsible for their desirableattributes. Without limiting the scope of the claims, some of theadvantageous features will now be summarized.

In some embodiments, a fluid turbine system comprises a turbine, aconcentrator, and a variable concentrator. The turbine comprises a bladeassembly, the blade assembly comprising a plurality of blades rotatableabout an axis. One or more of the blades defines an open sectionpositioned such that a portion of the open section is closer to the axisthan an outside edge of the blade. The turbine also comprises a pushhalf and a return half for a given direction of an overall flow of afluid that defines an upstream direction and a downstream direction. Theconcentrator is positionable in a concentrator position directlyupstream of at least a portion of the return half of the turbine. In theconcentrator position, the concentrator defines a convex surface facingupstream and a concave surface facing downstream. The convex surface ispositionable to deflect at least some fluid toward the push half of theturbine and the concave surface is positionable to redirect at leastsome fluid flowing generally upstream from the return half of theturbine to flow generally downstream. The variable concentrator ispositionable upstream of the turbine and closer to the push half thanthe return half. The variable concentrator comprises a deflectionsurface operable to deflect fluid, and the deflection surface ispositionable to extend generally parallel to the axis along asubstantial portion of a height of the turbine. The variableconcentrator is moveable between a first position and a second position,and the variable concentrator is configured to deflect more fluid towardthe blade assembly in the first position than in the second position.

In some embodiments, a fluid turbine system comprises a turbine and aconcentrator. The turbine comprises blades rotatable about an axis, andthe blades define a window along a substantial portion of a height ofthe blades. A first plane parallel with and intersecting the axisdivides the space surrounding the turbine into a return side and a pushside opposite the return side, and the turbine is configured to rotategenerally in an upstream direction on the return side and generally in adownstream direction on the push side relative to a fluid flowingnominally parallel to the plane. The concentrator is positionableupstream of at least a portion of the turbine and at least partially orcompletely on the return side. The concentrator comprises a first curvedsurface portion configured to extend from a first position upstream ofthe turbine to a second position further upstream of the turbine andfurther into the return side. The first curved surface portion isconfigured to be convex facing an upstream direction of the fluid flowand is positionable to deflect at least some fluid toward the push side.The concentrator is also positionable to create a relative vacuum todraw at least some fluid away from the window of the blades.

In some embodiments, a fluid turbine system comprises a turbine and aconcentrator. The turbine is rotatable about an axis, and a planeparallel with and intersecting the axis divides the space surroundingthe turbine into a return side and a push side opposite the return side.The turbine is configured to rotate generally in an upstream directionon the return side and generally in a downstream direction on the pushside relative to a fluid flowing nominally parallel to the plane. Theturbine has a return outer edge furthest away from the push side. Theconcentrator is positionable upstream of at least a portion of theturbine and at least partially or completely on the return side. Theconcentrator comprises a generally u-shaped section, and the generallyu-shaped section comprises an upstream surface portion positionable tobe convex facing upstream and a downstream surface portion positionableto be concave facing downstream. The upstream surface portion ispositionable to direct a push portion of fluid toward the push side andto direct a return portion of fluid downstream away from the turbine.The downstream surface portion forms a partially enclosed area shapedand positionable to receive a drag portion of fluid from the turbine andredirect the drag portion of fluid downstream into the return portion offluid. The concentrator has a return end configured to be furthest awayfrom the push side. The return end is positionable such that the closestdistance between the return end of the concentrator and the plane is atleast 1.2 times greater than the closest distance between the returnouter edge of the turbine and the plane.

In some embodiments, a fluid turbine system comprises a turbine and avariable concentrator. The turbine is rotatable about an axis. A firstplane parallel with and intersecting the axis divides the spacesurrounding the turbine into a return side and a push side opposite thereturn side. The turbine is configured to rotate generally in anupstream direction on the return side and generally in a downstreamdirection on the push side relative to a fluid flowing nominallyparallel to the plane. The turbine also defines a sweep path. Thevariable concentrator is positionable on the push side and upstream ofthe entire sweep path of the turbine. The variable concentratorcomprises a deflection surface positionable to extend generally parallelto the axis along a substantial portion of a height of the turbine. Thedeflection surface is adapted to deflect at least some fluid. Thevariable concentrator is moveable between a first position and a secondposition, and the deflection surface is configured to deflect less fluidtoward the turbine in the second position than in the first position.

In some embodiments, a fluid turbine comprises a plurality of bladesrotatable about an axis. One or more of the blades defines an opensection positioned such that a portion of the open section is closer tothe axis than an outside edge of the blade. The turbine comprises a pushhalf and a return half for a given direction of an overall flow of afluid that defines an upstream direction and a downstream direction. Oneor more of the plurality of blades is a push blade, the push bladedefining the open section and comprising a tip. The push blade ispositionable in a push position in which the tip of the push blade islocated on the push half. The push blade further comprises a pushsurface portion facing generally upstream when the push blade is in thepush position. One or more of the plurality of blades is a catch blade,the catch blade comprising a tip. The catch blade is positionable in acatch position in which the tip of the catch blade is located generallydownstream of the axis. The catch blade further comprises a catchsurface portion facing generally upstream when the catch blade is in thecatch position. The turbine is positionable in a torque position whereinan upstream blade is a push blade in the push position and a downstreamblade is a catch blade in the catch position. The torque position isdefined by the downstream blade being located generally downstream ofthe upstream blade and the catch surface portion of the downstream bladebeing located directly downstream from the open section of the upstreamblade.

The disclosure also includes methods of using and methods of manufactureof the systems and/or various components or combinations of componentsdescribed above or elsewhere herein.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects and advantages of the inventions willbe better understood with reference to embodiments illustrated in theaccompanying drawings. The illustrated embodiments are not intended todefine the limits or scope of the inventions.

FIG. 1 is a schematic illustrating an embodiment of a fluid turbinesystem.

FIG. 2 is a top view of the fluid turbine system of FIG. 1 illustratingvarious possible flow paths of a fluid.

FIG. 3 is a top view of the fluid turbine system of FIG. 1 illustratingvarious possible velocity zones.

FIG. 4 is a top view of the fluid turbine system of FIG. 1 showingvarious possible pressure zones.

FIG. 5 is a top view of the fluid turbine system of FIG. 1 with avariable concentrator showing possible fluid flow paths at low speed.

FIG. 6 is a top view of another embodiment of a fluid turbine systemwithout a variable concentrator illustrating various possible velocityzones.

FIG. 7 is a perspective view of components of an embodiment of a fluidturbine system with a blade assembly, a concentrator, and a variableconcentrator.

FIG. 8 is a side view of a fluid turbine system including the componentsof FIG. 7 and also illustrating a tail fin.

FIG. 9 is a perspective view of a blade assembly of the fluid turbinesystem of FIG. 8.

FIG. 10 is a front view of the blade assembly shown in FIG. 9.

FIG. 11 is a perspective view of the concentrator of the fluid turbinesystem of FIG. 8.

FIG. 12 is a perspective view of the variable concentrator of the fluidturbine system of FIG. 8.

FIG. 13 is a perspective view of another embodiment of a blade assembly.

FIG. 14 is a front view of a blade assembly shown in FIG. 13.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Although certain preferred embodiments and examples are disclosed below,inventive subject matter extends beyond the specifically disclosedembodiments to other alternative embodiments and/or uses and tomodifications and equivalents thereof. Thus, the scope of the claimsappended hereto is not limited by any of the particular embodimentsdescribed below. For example, in any method or process disclosed herein,the acts or operations of the method or process may be performed in anysuitable sequence and are not necessarily limited to any particulardisclosed sequence. Various operations may be described as multiplediscrete operations in turn, in a manner that may be helpful inunderstanding certain embodiments; however, the order of descriptionshould not be construed to imply that these operations are orderdependent. Additionally, the structures, systems, and/or devicesdescribed herein may be embodied as integrated components or as separatecomponents. For purposes of comparing various embodiments, certainaspects and advantages of these embodiments are described. Notnecessarily all such aspects or advantages are achieved by anyparticular embodiment. Thus, for example, various embodiments may becarried out in a manner that achieves or optimizes one advantage orgroup of advantages as taught herein without necessarily achieving otheraspects or advantages as may also be taught or suggested herein.

FIG. 1 is a schematic view illustrating an embodiment of a fluid turbinesystem 100. The turbine system 100 can include a blade assembly 140, aconcentrator 120, a variable concentrator 110, a guide motor 102, a tailfin 104, a gearbox 106, and a generator 108. In the embodimentillustrated in FIG. 1, the blade assembly 140, concentrator 120, andvariable concentrator 110, are positioned according to one possibleconfiguration of the turbine system. A hypothetical overall fluid flowfrom the top of FIG. 1 to the bottom of FIG. 1 defines an “upstream” anda “downstream” direction. The concentrator 120 and variable concentrator110 are located upstream of the blade assembly 140 as shown in FIG. 1.The overall fluid flow direction is for ease of description and aids indefining the structure of the turbine system. One of skill in the artrecognizes that an actual fluid may not flow consistently and uniformlyin a single direction.

The blade assembly 140 can comprise a plurality of blades. Asillustrated in FIG. 1, four blades 142, 144, 146, 148 are rotatableabout an axis Y corresponding to a center axis of a central shaft 190.The overall fluid flow direction also defines a blade rotationdirection. The blade assembly 140 shown in FIG. 1 will tend to rotatecounterclockwise in response to a fluid flowing in the overall fluidflow direction. As illustrated in the top view of the blade assembly 140shown in FIG. 1, each of the four blades can have an identicalcross-section. Each blade has a tip 150, 152, 154, 156. The blade tips150, 152, 154, 156 define a radius that the blade tip is located fromthe axis Y, which can be called the blade tip radius. Each blade 142,144, 146, 148 has a front side and a back side, on either side of tip150, 152, 154, 156. Most of the front side of blades 142, 144, 146, 148will face away from the blade rotation direction, and most of the backside will face toward the blade rotation direction.

The cross section of each blade shown in FIG. 1 has a substantiallystraight section 158, 160, 162, 164 extending along a tangent of thecentral shaft 190. The straight sections 158, 160, 162, 164 of theblades can include an open section or windows extending along a heightof the blades (shown in broken lines in FIG. 1, see also FIG. 9). Insome embodiments, the open sections of the blades extends along asubstantial portion of a height of the blades. The blades need notinclude substantially straight sections. Especially in embodiments wherethe substantially straight section of a cross-section of the bladecorresponds to the open section of the blade, the geometry of the bladesupport may have little effect on the movement of fluid around theblade. However, for ease of manufacturing and conservation of material,the blade supports along an open section can be substantially straight.The open sections can be continuous or discontinuous along the height ofthe blades. In some embodiments, each blade has an open section. Theopen section can be positioned such that a portion of the open sectionis closer to the axis Y than an outside edge of the blade. In someembodiments, approximately an inner radial half of the blade assembly issubstantially open such that the blades have little or no surface areaexposed to fluid within approximately an inner radial half of the bladeassembly. The open area may be smaller or larger depending on desiredtorque and drag characteristics. Open sections closer to the axis thanan outside edge of the blades can allow fluid to impart an impulse onthe portion of the blade that provides the most torque (i.e., furtherfrom the axis) and reduce drag created by fluid located near the axis ofrotation.

For purposes of discussion, a plane X is shown in FIG. 1 as a line.Plane X is parallel with and intersecting the axis Y about which theblades are rotatable, and parallel with the overall fluid flow. Plane Xdivides the space surrounding the turbine assembly generally into twohalves: the push side and the return side. Blade 144 is on the push sidebecause a fluid flowing in the direction of overall fluid flow asdefined above tends to rotate the blade assembly such that blade 144 ispushed by fluid and rotates in a downstream direction from the positionshown in FIG. 1. Blade 148 is on the return side because blade 148 willtend to rotate upstream to return back to the push side in response to ahypothetical overall fluid flow defined above for FIG. 1. The turbineitself can also have two halves: a push half and a return half. For agiven direction of an overall flow of a fluid that defines an upstreamdirection and a downstream direction, the push half of the turbine tendsto rotate upstream and the return half of the turbine tends to rotatedownstream.

With further reference to FIG. 1, a number of blade positions can bedefined in order to facilitate description of the geometry of blades142, 144, 146, 148 as well as their operation. Blade 142 can beconsidered to be in a lift position. The lift position is characterizedby a blade positioned such that a tip of the blade is located generallyupstream of the axis Y and a curved surface portion of the blade isconvex facing away from the return side. The tip 150 of blade 142 asillustrated in FIG. 1 is located upstream of the axis Y and a curvedsurface portion 166 is convex facing away from the return side. Blade144 can be considered to be in a push position. The push position can becharacterized by a blade position such that the tip of the blade islocated on the push side and a push surface portion of the blade facesgenerally upstream. Blade 144 has a tip 152 on the push side and a pushsurface portion 172 facing generally upstream. Blade 146 can beconsidered to be in a catch position. The catch position can becharacterized by a blade positioned such that the tip of the blade islocated generally downstream of the axis Y and a catch surface portionof the blade faces generally upstream. A tip 154 of blade 146 is locatedgenerally downstream of the axis Y and a catch surface portion 182 ofblade 146 is facing generally upstream as illustrated in FIG. 1. Blade148 can be considered to be in a return position. The return positioncan be characterized by a tip located on the return side and a returnsurface portion of the blade facing generally upstream. As illustratedin FIG. 1, blade 148 has a tip 156 located on the return side and areturn surface portion 184 facing generally upstream.

Based on the position of the blades as illustrated in FIG. 1, blade 142can be called a lift blade, blade 144 can be a called push blade, blade146 can be called a catch blade, and blade 148 can be called a returnblade. As the blade assembly 140 tends to rotate in a counterclockwisedirection, blade 142 will transition into a push position, blade 144will transition into a catch position, blade 146 will transition into areturn position, and blade 148 will transition into a lift position.These positions are used for description purposes, and each blade can beconsidered to be in more than one position at any given point in therotation of a given blade assembly. Each blade can also exhibitcharacteristics of one or more of a lift blade, a push blade, a catchblade, or a return blade at one or more points in its rotation about theaxis Y, including simultaneously exhibiting two or more characteristicsof such blades.

As discussed above, blade 142 is in the lift position. Blade 142 ispositioned and shaped to provide lift when acted on by a fluid, therebyproviding torque to rotate the blade assembly 140. The curved surfaceportion 168 of blade 142 as illustrated in FIG. 1 extends from a firstend 166 near the tip 150 of blade 142 to a second end 170 near thegenerally straight section 158 or open section of blade 142.

Blade 144 is in the push position, with push surface portion 172 facinggenerally upstream. As illustrated in FIG. 1, push surface portion 172can be generally straight and located on a front surface of blade 144.The front surface of blade 144 can also include a curved portion 174located further from the central shaft 190 radially from the pushsurface portion 172. As illustrated in the position of blade 144 shownin FIG. 1, the curved portion 174 is located further upstream than thepush surface portion 172 when the push surface portion 172 is generallyperpendicular to plane X. Blade 144 also includes a back surface portion178 located opposite the curved portion 174 and the push surface portion172. The back surface portion 178 extends from a first end 176 near thetip 152 of blade 144 to a second end 180 near the generally straightsection 160 of blade 144. As illustrated in FIG. 1, blade 144 is in ahorizontal position. The back surface portion 178 of blade 144 is convexfacing downstream. The back surface portion is also shaped andconfigured such that a middle portion of the back surface portion 178extends further downstream than the first end 176 and the second end 180of the back surface portion 178 when blade 144 is in the horizontalposition. Because the back surface portion is located on approximatelyan outer radial half of blade 144 in the embodiment illustrated in FIG.1, the middle portion of the back surface portion 178 is also locatedoutside of an inner radial half of blade 144. The middle surface portionof the back surface portion 178 can reduce drag and provide lift invarious positions of the blade, and these features can be enhanced bythe location of the middle surface portion near the tip of a blade.Additional, features of the blades 142, 144, 146, 148 of the bladeassembly 140 are described below.

As illustrated in the schematic of FIG. 1, the blade assembly 140 can beconnected to a gearbox 106 and/or a generator 108. In some embodiments,the gearbox 106 is used to convert the speed of rotation of the bladeassembly 140. The generator 108 can be connected to the gearbox 106 orto the blade assembly 140 to convert rotational energy of the turbinesystem 100 into electrical power. The fluid turbine system 100 can beused without a gearbox 106 or a generator 108 to perform other functionsor produce other forms of energy such as mechanical energy for use indriving a mechanical device.

The concentrator 120 illustrated in FIG. 1 will now be described. Theconcentrator 120 includes an upstream surface and a downstream surface.The concentrator can also include a push end 134 located closest to thepush side or furthest from the return side and a return end 128 locatedfurthest into the return side or furthest from the push side. In theembodiment shown in FIG. 1, the concentrator is shaped substantially asa front section of an airflow with a hollow or open downstream side. Theupstream surface can include a first curved surface portion 122extending from a first position upstream of at least a portion of theturbine to a second position further upstream and further into thereturn side. The first curved surface portion 122 of the upstreamsurface can be shaped to be convex facing generally upstream andpositionable to deflect at least some fluid toward the push side of theturbine system.

In the embodiment illustrated in FIG. 1, the push end 134 of theconcentrator 120 is located on the return side of plane X. In FIG. 1,the push end 134 is an end of the concentrator 120 closest to the pushside but a gap remains between push end 134 and plane X. A gap betweenthe push end 134 and plane X can increase efficiency, power, or minimumstartup fluid speed of the system. For example, fluid flowing in adirection toward the push side from the concentrator 120 (e.g., fromfirst curved surface portion 122) can begin to “push” blade 142 in theproper direction sooner than if the push end 134 of the concentratorwere positioned closer to the push side or if no concentrator 120 werepresent. As blade 142 rotates counterclockwise from the position shownin FIG. 1, fluid flowing downstream and/or toward the push side from theconcentrator 120 can impinge upon the front side of blade 142 soonerthan the front side of blade 142 would otherwise be exposed to fluidapproaching blade 142 in the direction of the overall fluid flow. Insome embodiments, the gap or a shortest distance between the push end134 of the concentrator 120 and plane X is greater than about onepercent (1%) of the blade tip radius, greater than about three percent(3%) of the blade tip radius, or greater than about five percent (5%) ofthe blade tip radius. In some embodiments, the gap is between about sixand seven percent of the blade tip radius. However, the push end 134 ofconcentrator 120 need not be located on the return side of plane X.

In some embodiments, the concentrator 120 is positioned such that atleast a portion of the concentrator 120 is on the push side of theturbine system 100. The concentrator 120 can also intersect plane X whenin this position. A gap can also exist between the push end 134 of theconcentrator 120 and plane X such that the concentrator 120 at leastpartially blocks the blade assembly 140 on the push side. It can bedesirable to position the concentrator 120 to at least partially blockthe blade assembly 140 on the push side in order to slow rotation of theblade assembly 140, stop rotation of the blade assembly 140, or protectthe turbine system 100 from damage by fluid flowing at high speeds. Insome embodiments, when the push end 134 of the concentrator 120 is onthe push side, a blocking gap exists between the push end 134 and planeX. The blocking gap can be greater than about one percent (1%) of theblade tip radius, greater than about three percent (3%) of the blade tipradius, or greater than about five percent (5%) of the blade tip radius.The blocking gap can be between about twenty-five percent and aboutfifty percent of the blade tip radius. In some embodiments the blockinggap is greater than about fifty percent of the blade tip radius. In someembodiments the blocking gap can be about 100 percent of the blade tipradius. In some embodiments, a center of the concentrator 120 ispositionable to approximately intersect plane X.

In some embodiments, the concentrator 120 is moveable between a firstposition and a second position. The second position can correspond to aposition in which the turbine system 100 is configured to extract lessenergy from the fluid or expose less of the blade assembly 140 to fluidapproaching the turbine system 100 than in the first position. In someembodiments, when the concentrator 120 is in the first position, thepush end 134 and the return end 128 of the concentrator 120 are on thereturn side of the turbine system 100. In some embodiments, when theconcentrator 120 is in the second position, the push end 134 is on thepush side and the return end 128 is on the return side. The concentrator120 can also be positionable to fully block the blade assembly 140 fromsubstantially any direct exposure to fluid approaching the turbinesystem 100. In some embodiments, the concentrator 120 is moveable alonga track between the first and the second positions. A motor can be usedto adjust the position of the concentrator 120. A sensor mounted on ornear the fluid turbine system 100 can be used to sense a direction orspeed of the fluid. Information from the sensor can be used to manuallyor automatically adjust the position of the concentrator 120. Forexample, a sensor mounted on the concentrator 120 can send a signal to acomputer indicating a high fluid or wind speed. The computer candetermine that the concentrator 120 should be moved to reduce therotational speed of the blade assembly 140 or to protect the bladeassembly 140 from damage. As wind speed decreases, the concentrator 120can be automatically moved back toward the first position. Theconcentrator 120 can be a governor, which governs the rotational speedof the blade assembly 140. Movement of the concentrator 120 can beinstead of, in addition to, or combined with adjustment of theconcentrator with respect to an overall fluid flow direction asdescribed elsewhere herein.

The upstream surface of the concentrator 120 can also include a secondsurface portion 126 positionable further into the return side relativeto the first curved surface portion 122. The second surface portion canextend from a third position to a fourth position that is further intothe return side and further downstream than the third position. Theconcentrator can have a deflection point 124 at which fluid is eitherdeflected toward the push side or away from the push side. Theconcentrator 120 can be symmetrical as shown in the embodimentillustrated in FIG. 1, in which case the deflection point 124 can be themidpoint of the upstream surface. As shown in FIG. 1, the upstreamsurface portions on either side of the deflection point 124 can beconvex facing upstream such that the entire upstream surface is agenerally U-shaped surface that is convex facing upstream. The upstreamsurface can have a generally parabolic shape, which may or may notconform mathematically to a parabolic equation. The upstream surface asa whole can also be generally shaped as the leading end of an airfoil,which may or may not technically conform to a strict mathematicaldefinition of an airfoil. As used throughout, the terms “parabola” and“airfoil” are broad terms, and the shaped surfaces these terms describeneed not conform strictly to a mathematical definition of a “parabola”or “airfoil” shape.

The downstream surface of the concentrator 120 can be shaped andpositioned to be concave facing downstream. In the embodimentillustrated in FIG. 1, the downstream surface of concentrator 120includes an upstream flow surface 132, an intermediate surface 136, anda downstream flow surface 130. As will be discussed with reference toFIG. 2, the upstream flow surface 132 can be configured to receive fluidflowing upstream from the blade assembly 140 and direct the fluid towardthe intermediate surface 136. The intermediate surface 136 can beconfigured to redirect at least some fluid from the upstream flowsurface 132 to the downstream flow surface 130. The downstream flowsurface 130 is shaped and configured to direct fluid downstream into theoverall flow of fluid to eventually flow away from the blade assembly140. As illustrated in the embodiment shown in FIG. 1, the downstreamsurface of the concentrator 120 can be substantially equidistant fromthe upstream surface of the concentrator 120, forming a concentrator 120of substantially constant thickness. In some embodiments, theconcentrator 120 as a whole can be shaped generally as a parabola,shaped generally as the leading end section of a substantially hollowairfoil, or be generally U-shaped. The concentrator 120 can also extenda distance Z past an outer end of a path of the blades on the returnside, as shown in FIG. 1 and further described below.

The variable concentrator 110 illustrated in FIG. 1 will now bedescribed. The variable concentrator 110 can be shaped generally as anairfoil. As illustrated in FIG. 1, a variable concentrator 110 has aleading edge 112, a trailing edge 118, and two side surfaces 114, 116.The variable concentrator 110 is located on the push side of the turbinesystem and upstream of the blade assembly 140. Side surface 114 can be adeflection surface that extends generally parallel to the axis Y along asubstantial portion of a height of the blade assembly 140.

The variable concentrator 110 can be movable between a first positionand a second position, and the variable concentrator 110 can beconfigured to deflect more fluid toward the blade assembly in the firstposition than in the second position. In some embodiments, the variableconcentrator 110 is biased towards the first position by a biasingmechanism. The biasing mechanism may be active (e.g., a motor) orpassive (e.g., a spring). As a speed of a fluid flowing past thevariable concentrator 110 increases, the variable concentrator can movetowards the second position in which less fluid or substantially nofluid is deflected toward the blade assembly 140. In some embodiments,the fluid flowing across the variable concentrator 110 causes thevariable concentrator 110 to move. In some embodiments, a motor or otherpositioner can be used to position the variable concentrator 110 insteadof or in addition to movement caused by the fluid flowing past thevariable concentrator 110. The turbine system 100 can be configured toposition the variable concentrator in the first position in low fluidspeed environments and in the second position in high fluid speedenvironments. The variable concentrator can deflect fluid toward theblade assembly in low fluid speed environments and prevent high fluidspeeds from damaging the turbine. Accordingly, the variable concentratorcan also be called a governor.

The schematic shown in FIG. 1 includes a guide motor 102 and a tail fin104 as part of the fluid turbine system 100. The guide motor 102 and thetail fin 104 can be used alone or in combination to maintain a relativeposition of one or more of the concentrator 120 and variableconcentrator 110 generally upstream of the blade assembly 140. In someembodiments, the concentrator 120 is shaped and configured such that itautomatically maintains a position upstream of blade assembly 140 androtates around the outer perimeter of blade assembly 140 to maintain itsupstream position. For example, as shown in FIG. 1, the curvedsymmetrical shape of the concentrator 120 can allow it to tend to faceupstream into a fluid flow. In embodiments where one or more of theconcentrator 120 or variable concentrator 110 are shaped and configuredto face upstream in a given fluid flow, another of the variableconcentrator 110, concentrator 120, or other components of the fluidturbine system can be coupled to the moveable component to also maintaina specified position in relation to the upstream direction. In someembodiments, the turbine system can be deployed in areas with agenerally constant fluid (e.g., wind) direction and the concentrator 120and variable concentrator 110 can have a relatively fixed position inrelation to the blade assembly 140.

FIG. 2 is an example embodiment of a turbine system that includes ablade assembly 140, a concentrator 120, and a variable concentrator 110.The general direction of overall fluid flow is shown by arrows 200. FIG.2 shows generally various possible fluid flow paths around the turbinesystem in response to an overall fluid flow approaching the turbinesystem as shown by arrows 200. For example, arrow 204 shows that somefluid can be directed toward the push side as shown in FIG. 2. Arrow 206indicates that at least some fluid can be directed away from the pushside and continue downstream eventually to flow away from the turbinesystem. Arrow 208 indicates that at least some fluid can flow across aback surface portion 250 of blade 142. As fluid flows across the backsurface portion 250 of blade 142, the fluid velocity can increase. Anincrease in velocity of the fluid flowing along the path shown by arrow208 can provide lift to blade 142, thereby providing torque that tendsto rotate the blade assembly 140. Fluid flowing along the concentrator120 (e.g., along paths indicated by arrows 204, 206) also tends toincrease in velocity and compress. The compressed, concentrated fluidsped up by the concentrator 120 along the path indicated by arrow 204flows into the push side, thereby providing more torque to rotate theblade assembly 140.

An outer perimeter of a sweep path of the blade assembly 140 is shown bybroken line 202. As shown by arrows 214, 216, 218, 220 in FIG. 2, fluidwithin the sweep path of the blade assembly 140 can flow in acounterclockwise direction. Fluid flowing along the path indicated byarrow 214 can provide an impulse to the push surface 260 of blade 144.Fluid flowing along the path indicated by arrow 216 can provide animpulse to the catch surface 270 of blade 146. Concentrator 120 can beshaped, configured, and/or positioned such that the overall fluid flowwill not act upon a drag surface 280 of blade 148. In the embodimentillustrated in FIG. 2, the portion of the concentrator located furthestinto the return side extends beyond the sweep path in a directionperpendicular to plane X and away from the push side. Fluid flowing pastthe concentrator 120 along a path indicated by arrow 206 thus tends toflow downstream past the blade assembly 140 without impinging upon thedrag surface 280 of blade 148, thereby increasing efficiency of theturbine system.

As indicated by arrows 224, 226, 228, 230, 232, the shape and positionof the concentrator 120 can also cause fluid flowing upstream out of thesweep path of the blade assembly 140 to be redirected by concentrator120 to flow downstream and eventually away from the blade assembly 140.In particular, fluid can flow along a path indicated by arrow 228 alongan upstream flow surface 132 of the concentrator 120 and be redirectedto flow downstream along a path indicated by arrow 230 along adownstream flow surface 130 of concentrator 120. Concentrator 120 canthereby provide a fluid escape path which continuously draws fluid awayfrom the blade assembly 140. This continuous draw of fluid can create orcontribute to a relative vacuum effect which tends to remove fluid fromthe sweep path of the blade assembly after the fluid has imparted animpulse to the blades.

As described above, an end of concentrator 120 can extend beyond a sweeppath of the blades in a direction perpendicular to plane X and away fromthe push side, as shown by distance Z in FIG. 1. The positioning of theconcentrator can thus create a blocking effect which not only preventsfluid flowing downstream from contacting blade 148, but can provideenough space for fluid to be drawn up into the concentrator withoutflowing against the overall fluid flow (e.g., along a path indicated byarrow 224). As fluid leaves the downstream flow surface 130 of theconcentrator 120 (e.g., along a path indicated by arrow 232) it can joinor flow alongside fluid which has been deflected from an upstreamsurface of the concentrator 120 (e.g., along a path indicated by arrow206). In some embodiments, the concentrator 120 extends in a directionfurther into the return side at least to an outer edge of the turbinesuch that the concentrator at least intersects a second plane tangent toan outermost edge of the turbine and parallel to plane X. The secondplane can be separated from plane X by a blade tip radius, and theconcentrator can extend past the second plane by an extension distancemeasured in a direction perpendicular to plane X and away from the pushside. In some embodiments, the extension distance can be at least five,at least ten, at least twenty, at least twenty-five, or at least thirtypercent of the blade tip radius. In some embodiments, the extensiondistance is between about ten and about twenty percent of the blade tipradius. Preferably, the extension distance is between about twenty andthirty percent of the blade tip radius, between about twenty-three andtwenty-seven percent of the blade tip radius, or about twenty-fivepercent of the blade tip radius. In some embodiments, the turbine has areturn outer edge furthest away from the push side and the concentratorhas a return end furthest away from the push side. In some embodiments,the closest distance between the return end of the concentrator andplane X is at least 1.1, at least 1.2, at least 1.3, at least 1.4, or atleast 1.5 times greater than the closest distance between the returnouter edge of the turbine and plane X. Preferably, the closest distancebetween the return end of the concentrator and plane X is between about1.1 and 1.4, between about 1.2 and 1.3, or about 1.2 times greater thanthe closest distance between the return outer edge of the turbine andplane X.

The relative vacuum effect that can be created by the concentrator 120can also cause a center of rotation of fluid near the blade assembly 140to shift toward the return side or further into the return side. Thegeneral direction of fluid flowing in the open sections or windows ofthe blades is shown by arrows 234, 236, 238, 240. This fluid can bedrawn out away from the blade assembly by the concentrator 120 as shownin part by arrows 242, 244. Arrows 221 and 222 indicate that at leastsome fluid can escape the sweep path of the blade assembly 140 and flowgenerally downstream away from the turbine system without being drawnfully toward the downstream surface of the concentrator and redirectedaway from the concentrator.

In the embodiment of the turbine system illustrated in FIG. 2, thevariable concentrator 110 is positioned such that it deflects little orno fluid toward the blade assembly 140, or only a small amount of fluid,no more fluid, or slightly less fluid than would flow toward the bladeassembly 140 due to the overall fluid flow defined by arrows 200 in theabsence of the variable concentrator 110. In some embodiments, fluidflowing along the side surfaces of the variable concentrator (e.g.,along paths indicated by arrows 210, 212) can increase in speedtemporarily, but is not directed further toward the blade assembly 140than the overall flow of fluid. In some embodiments, the variableconcentrator 110 is shaped and positioned such that when it is notdirecting fluid toward the blade assembly 140 it provides a slightblocking effect to prevent high fluid speeds from damaging the bladeassembly 140.

With further reference to FIG. 2, the blade assembly 140 in the positionillustrated in FIG. 2 has a blade 142 in the lift position, a blade 144in the push position, a blade 146 in the catch position, and a blade 148in the return position. In some embodiments, a blade assembly 140 has atorque position in which at least one blade is in a lift position, atleast one blade is in a push position, at least one blade is in a catchposition, and at least one blade is in a return position. As the bladeassembly 140 rotates, the blades can change positions. In someembodiments, the blade assembly 140 is always in a torque position as itrotates, such that favorable torque characteristics of the liftposition, the push position, the catch position, and the return positionare constantly exhibited as the turbine rotates in response to an inputfluid. In some embodiments, each blade is primarily only in one of thelift position, push position, catch position, and return position. Insome embodiments with four blades, for one or more rotational positionsof the blade assembly 140 there is only one lift blade, one push blade,one catch blade, and one return blade, the blades being categorized bytheir primary or dominant position.

FIG. 3 is a top view of a turbine system similar to that shown in FIG. 2and illustrates various zones of relative velocity of fluid flowingalong the paths illustrated in FIG. 2 resulting from the describedfeatures. Zones A, B, C, D and E illustrate areas of a relatively mediumfluid velocity. Zones F and G indicate zones of relatively high fluidvelocity. Zones H, I, J, K, L, and M illustrate zones of relatively lowvelocity.

In FIG. 3, Zones A, B, C, D, and E have a fluid velocity near the inputvelocity. Zones F and G have fluid velocities greater than the inputvelocity, while Zones H, I, J, K, L, M have fluid velocities below theinput velocity. In FIG. 3, an input velocity near 28 mph can createvelocities of at least 45 mph as shown in Zone F near the push side ofthe blade assembly.

FIG. 4 is a top view of a turbine system showing various zones ofrelative pressure of a fluid surrounding the turbine system. Assuming adirection of overall fluid flow as shown in FIG. 2, the turbine systemillustrated in FIG. 4 can have medium pressure zones shown as Zones N,O, P, Q, R, and S in FIG. 4. The turbine system can have a high pressurezone shown as Zone T and a lower pressure zone indicated as Zone U inFIG. 4.

FIG. 5 illustrates another embodiment of a turbine system 100. In FIG. 5the variable concentrator 110 is positioned to deflect fluid toward theblade assembly. In particular, at low fluid (e.g., wind) speeds, avariable concentrator positioned to deflect fluid toward the bladeassembly can decrease a startup fluid speed of the turbine system andincrease efficiency of the system at low fluid speeds. Fluid can flowaround the variable concentrator 110 as indicated by arrows 510, 520.The shape of the variable concentrator 110 can cause the fluid toincrease in velocity and compress as it flows around the variableconcentrator 110. The variable concentrator 110 can also be positionedsuch that fluid leaving the variable concentrator 110 can then flowalong the path as indicated by arrow 550 toward the blade assembly. Atleast some of this fluid can act on one or more of the blades 142, 144,146, 148 of the blade assembly, and in particular on a push surface 260of blade 144 in the blade position illustrated in FIG. 5.

In some embodiments, various features of the fluid turbine system 100can increase torque output of the system or decrease a speed of fluidneeded to begin rotating the blade assembly. For example, when the bladeassembly is stationary in the position illustrated in FIG. 5, a fluidcan provide torque from at least blades 142, 144, and 146. Inparticular, fluid flowing across the curved surface portion 250 of blade142 as indicated by arrow 560 can create a lift effect tending to rotateblade 142. At least some fluid can also flow through the open section ofblade 144 located near the generally straight section 160 of blade 144and act on the catch surface 270 of blade 146. When the catch surface270 is located directly downstream from the open section of blade 144,fluid flowing directly downstream can flow through the open section ofblade 144 and against the catch surface 270 of blade 146. In someembodiments, e.g., as shown in FIG. 5, fluid deflected by other surfacesof the turbine system 100 (e.g., surfaces on variable concentrator 110or on curved surface portion 250 of blade 142) causes fluid to veer fromthe direction of the overall fluid flow and impinge against portions ofblade 146 not located directly downstream from the open section of blade144. Fluid from the overall fluid flow or directed towards the bladeassembly from the variable concentrator 110 can also act on the pushsurface portion 260 of blade 144. Accordingly, a flow of fluid acrossthe blade assembly stationary in the position of FIG. 5 can providetorque from at least three of the blades illustrated in FIG. 5. Fluidflowing past a rotating blade assembly 140 can also provide torque fromat least three of the blades simultaneously.

As discussed above with reference to FIG. 2, the concentrator 120 shownin FIG. 5 can also block the overall fluid flow from creating additionaldrag on the drag surface 280 of blade 148. The concentrator 120 can alsoincrease the velocity of and compress the fluid flowing along a pathindicated by arrow 540. Fluid flowing away from the push side alongarrow 530 is also concentrated and compressed, which can aid in drawingfluid away from the blade assembly as described above with reference toFIG. 2.

FIG. 6 is a top view of a turbine system without a variableconcentrator. FIG. 6 indicates various velocity zones of fluid flowingaround the turbine system. The velocity of the input fluid is shown inZone A′. The input fluid has a velocity in the medium range, along withthe fluids in Zones C′, D′, and E′. The fluid in Zones F′ and G′ flowsat a higher velocity than the input fluid, and the fluid in Zones H′,I′, J′, K′, L′, and M′ flows at a lower velocity than the input fluid.

In FIG. 6, the input velocity is 28 mph with a maximum velocity of atleast 45 mph in Zone F′. Medium range velocity zones are designated asA′, C′, D′, and E′. High fluid velocity zones include F′ and G′. Lowfluid velocity zones include H′, I′, J′, K′, L′, and M′. The maximumspeed area in zone F′ of FIG. 6 is larger than the maximum speed area inzone F of FIG. 3, indicating that the variable concentrator and itsposition in FIG. 3 can reduce the amount of fluid flowing at maximumspeeds, thereby preventing damage to the turbine in high fluid speeds.

FIG. 7 shows an embodiment of a fluid turbine system 700. The fluidturbine system 700 comprises a blade assembly 740, a concentrator 720,and a variable concentrator 710. The blade assembly 740, concentrator720, and variable concentrator 710 can be similar to the blade assembly140, concentrator 120, and variable concentrator 110 described herein.In the embodiment illustrated in FIG. 7, the concentrator 720 andvariable concentrator 710 have a height that is substantially greaterthan a height of the blade assembly 740. In some embodiments, a heightof the blade assembly 740, concentrator 720, and variable concentratoris substantially equal. In some embodiments, a height of one or more ofthe concentrator 720 or variable concentrator is at least a substantialportion of a height of one or more blades of the blade assembly.

FIG. 8 is a side view of an embodiment of a vertical axis fluid turbinesystem 800. For purposes of discussion, the fluid direction is shown bythe arrow 810. Bearing cases 806, 808 at the top and bottom of a centralshaft 190 of a blade assembly 140 allow the blade assembly 140 torotate. The bearing case 806 can be mounted to an upper bracket 802, andthe bearing case 808 can be mounted to a lower bracket 804. In theembodiment illustrated in FIG. 8, the upper and lower brackets 802, 804can rotate relative to a base 812 at the bottom of the turbine system800. A tail fin 104 can extend between the upper and lower brackets 802,804. The tail fin 104 can orient the system such that a concentrator 120and variable concentrator 110 will be upstream (e.g., upwind) of theblade assembly 140 and face into an approaching fluid (e.g., wind). Thevariable concentrator 110 and the concentrator 120 extend between theupper and lower brackets 802, 804 on the left of the blade assembly asshown in FIG. 8. In some embodiments, the concentrator 120 is fixed inrelation to the upper and lower brackets 802, 804 and the variableconcentrator is rotatably fixed to the upper and lower brackets 802,804. In some embodiments, a gearbox 106 can be used to convert the speedof the rotation of the blade assembly 140 to a speed optimal forconverting rotational energy into electrical power. The gearbox 106 canbe located in the base 812 of the system.

A guide motor 102, which can be a servo motor, can also be used insteadof or in addition to the tail fin 104 to orient the upper and lowerbrackets 802, 804 in relation to the base 812. The guide motor 102 canbe connected to a sensor, which in some embodiments can sense thedirection of fluid flow (e.g., wind) and orient the turbine system 800such that the concentrator 120 and variable concentrator 110 areupstream (e.g., upwind) of the blade assembly. The guide motor 102 canbe used to stabilize the system and prevent the tail fin 104 fromoscillating or turning in response to slight changes in fluid flowdirection. In some embodiments, a damper (not shown) can be used insteadof or in addition to the guide motor 102 to slow the response of thesystem to minute changes in fluid flow direction. A second guide motor(not shown) can be used to orient the variable concentrator 110. Thesecond guide motor can be connected to a sensor which in someembodiments can sense fluid speed and orient the variable concentrator110 away from the blade assembly 140 when the system 800 is subjected tohigh fluid speeds (e.g., in high winds) to divert fluid away from theblade assembly 140. One or more of the guide motors can be locatedwithin the base 812. Other configurations of brackets or mountingmembers for the blade assembly 140, concentrator 120, and variableconcentrator 110 can be used. These designs can also be optimized topromote efficient conversion of fluid energy. In some embodiments, oneor more of the blade assembly 140, concentrator 120, or variableconcentrator 110 are mounted separately and may be separately moveablein relation to one or more of the other components. The fluid turbinesystem 800 can also include a starter. The starter can help to beginrotation of the blade assembly 140. In some embodiments, a starter isnot necessary and the blade assembly 140 will self-start in appropriatefluid conditions.

FIGS. 9-10 show a blade assembly 740 with four blades. Approximately aninner radial half of the blades is substantially open. A top bladesupport 902, middle blade supports 904, and a bottom blade support 906extend from an axis of rotation to a substantially solid portion of theblade located further from the axis than the open sections. As seen inFIGS. 9 and 10, an open section or window can extend along a substantialportion of a height of the blades. The open sections can be continuousor discontinuous. For example, opening 1002 in FIG. 10 can be a viewedas a continuous opening 1002 or a small section of a singlediscontinuous opening extending along a height of the blade.

FIG. 11 is a perspective view of the concentrator 720 shown in FIG. 7.The concentrator 720 comprises an upstream surface 1104 and a downstreamsurface 1106. A leading edge 1102 of the concentrator 720 is configuredto divide fluid flowing toward the concentrator 720 into a push portionof fluid to flow toward a push half of the turbine and a return portionof fluid to flow away from the push half of the turbine. Trailing edges1110, 1108 can be positionable downstream of the leading edge 1102.Trailing edge 110 can correspond to the push end 134 of the concentrator120 shown in FIGS. 1 and 2. Trailing edge 112 can correspond to thereturn end 128 of the concentrator 120 shown in FIGS. 1 and 2.

FIG. 12 is a perspective view of the variable concentrator 710 shown inFIG. 7. The variable concentrator 710 can have a leading edge 1202, atrailing edge 1206, and a side deflection surface 1204. Trailing edge1206 can be positionable downstream of leading edge 1202.

FIGS. 13-14 show an embodiment of a blade assembly 1300 that can beconfigured for use in a fluid turbine system similar to those describedabove. The embodiment of a blade assembly 1300 shown in FIG. 13 can besimilar to the embodiment depicted of the blade assembly 140 in FIG. 1,with the addition of horizontal plates mounted periodically along thelength of the blade assembly. As shown in FIG. 13, the blade assembly1300 can have seven sections, each with a horizontal plate at the topand bottom of the section. The blades can have an open section orwindows, which can be located near the central portion of each bladesection. FIG. 14 shows a front view of the blade assembly 1300, withopening 1402 near the central portion of the blade.

In some embodiments, the blade assembly 1300 can be modular. Forexample, each of the seven blade assembly sections can be a separatepiece mounted separately to a central shaft 1308. A modular bladeassembly can allow for ease of manipulation of the number of bladesections in a turbine system design based on user preferences oravailable space. One example method of assembling the blade assembly1300 can be as follows: (1) provide a central shaft 1308 with a bottomplate 1306 fixed to the shaft; (2) provide a blade assembly sectioncomprising a plate 1304 comprising blade sections projecting from theunderside of the plate 1304, the blade sections comprising an openingtoward the center of the plate 1304; (3) mounting the blade assemblysection to the central shaft 1308; and (4) mounting additional bladeassembly sections to the central shaft 1308, with the final bladeassembly section comprising top plate 1302. In some embodiments, one ormore blade assembly sections can comprise a plate 1304 at the bottom ofthe blade assembly section instead of the top. In some embodiments, thehorizontal plates can be separate from the blades, or could be omittedaltogether.

In some embodiments, one or more portions of the blade assembly can beoffset radially from one or more of the other portions. For example, theblades in one section of a modular blade assembly may not align with theblades in the section above and/or below it, unlike the blade assemblydepicted in FIG. 13 in which the blades of each section are aligned toeffectively form a straight blade along the height of the bladeassembly. Offsetting the blade sections can aid in creating a non-cyclictorque output. In some embodiments, each section of the blade assemblyis offset from the others by ten degrees. In some embodiments, eachsection is offset by between about 1 and about 20, between about 5 and15, or between about 8 and 12 degrees of a section below or above it. Insome embodiments, an even offset can be calculated based on the numberof blades in each section and/or the number of sections to evenly placeblades around the central shaft in various patterns. In someembodiments, the offset is not even among the different sections.

In some embodiments, the offset of the different blade sections cancreate a helical shape or “virtual helix.” For example, a blade 1322 atthe bottom section of the blade assembly 1300 can be mounted in areference position of 0 degrees relative to the central shaft 1308. Ablade 1320 in the next section can be mounted at 10 degrees, a blade1318 in the next section can be mounted at 20 degrees, etc. throughblade 1310 at the top of the blade assembly 1300. For a given rotationalorientation of blade assembly 1300, blades 1322, 1320, 1318, 1316, 1314,1312, 1310 will be located in different positions relative to a flow offluid and can capture an impulse from the fluid at different times. Ifeach section has four blades evenly spaced from each other, fourdifferent helical patterns can be seen as the blade assembly 1300rotates.

In some embodiments, the blade sections can be offset in a pattern suchthat the blade sections fan out in the same direction above and below aparticular blade section. The pattern can be similar to the helicalshape described above, except that it can consist of two discontinuoushelical shapes. For example, a blade 1316 of a central section of theblade assembly 1300 can be mounted in a reference orientation at 0degrees relative to the central shaft 1308. A blade 1314 in the nexthigher section can be mounted at 10 degrees. A blade 1312 in the nexthigher section can be mounted at 20 degrees. A blade 1310 in the nexthigher section can be mounted at 30 degrees. A blade 1318 in the sectiondirectly below blade 1316 can be mounted at 10 degrees. A blade 1320 inthe next lower section can be mounted at 20 degrees. A blade 1322 in thenext lower section can be mounted at 30 degrees. Fewer or additionalblade sections can be included, and the offset angles can vary. In someembodiments, a blade assembly 1300 can have blade sections withadjustable offset angles such that the offset pattern can be variedaccording to user preferences, fluid flow conditions, or other factors.The offset designs described above with reference to FIG. 13 can be usedwith the blade assembly 140 described with reference to FIG. 1. Theembodiments described in FIGS. 1-12 can also be modular and constructedin separate sections as described with reference to the embodiment shownin FIG. 13.

In some embodiments, fewer or additional concentrators or variableconcentrators can be configured for use with the blade assembly. Thatis, a blade assembly can be used alone, or in combination with one ormore of a concentrator or variable concentrator. When used incombination, the different components can enhance the favorablecharacteristics exhibited by the other, sometimes synergistically. Forexample, the use of a concentrator with a blade assembly comprisingopenings or windows towards an inner radial portion of the blades canincrease the effect of having a concentrator or having blade openingsalone. The turbine system can also include additional blade assemblies,and one or more of the blade assemblies can include lesser or more thanfour blades. In some embodiments, parameters of the design can beoptimized using computer simulation studies such as Cosmos FloWorksand/or ADINA computer modeling. PIV fluid mechanics analysis can also beemployed. These tools can be used to increase the efficiency of thedesign and confirm the desirability of modifications in the quantity,size, shape, and/or placement of the different components of the turbinesystem. A design similar to that illustrated in FIG. 3 can be estimatedto produce about 5 Kilowatts of power in an approximately 28 mile perhour wind. In some embodiments, a theoretical efficiency of over 30percent can be achieved. The higher the efficiency, the more availablepower from fluid flow is converted into useable energy, e.g., electricalpower. Some embodiments of the vertical-axis fluid turbine system canalso be configured not to require uni-directional or laminar fluid flow.The system can also produce a low amount of noise, even at high fluidflow speeds. Birds are less likely to be injured by turbine systemsdescribed herein. Many characteristics of embodiments of the fluidturbine systems described herein can make the systems desirable for useas wind turbines in urban environments, where they can also be mountedon pre-existing structures. The systems described herein can thereforebe used to exploit wind resources from niches unsuitable for other windturbines while still producing substantial amounts of power and reducingtransmission line losses.

Although the turbine systems described above are described withreference to vertical axis turbines, such systems need not be mountedvertically. Some embodiments can be mounted horizontally or in otherorientations with appropriate modifications. Moreover, certainindividual features or combinations of features disclosed herein may beadapted for use in horizontal turbines or other types of turbines. Inaddition, other fluids can be used to rotate the turbines in theabove-described systems, including water.

Reference throughout this specification to “some embodiments” or “anembodiment” means that a particular feature, structure or characteristicdescribed in connection with the embodiment is included in at least someembodiments. Thus, appearances of the phrases “in some embodiments” or“in an embodiment” in various places throughout this specification arenot necessarily all referring to the same embodiment and may refer toone or more of the same or different embodiments. Furthermore, theparticular features, structures or characteristics may be combined inany suitable manner, as would be apparent to one of ordinary skill inthe art from this disclosure, in one or more embodiments.

As used in this application, the terms “comprising,” “including,”“having,” and the like are synonymous and are used inclusively, in anopen-ended fashion, and do not exclude additional elements, features,acts, operations, and so forth. Also, the term “or” is used in itsinclusive sense (and not in its exclusive sense) so that when used, forexample, to connect a list of elements, the term “or” means one, some,or all of the elements in the list.

Similarly, it should be appreciated that in the above description ofembodiments, various features are sometimes grouped together in a singleembodiment, figure, or description thereof for the purpose ofstreamlining the disclosure and aiding in the understanding of one ormore of the various inventive aspects. This method of disclosure,however, is not to be interpreted as reflecting an intention that anyclaim require more features than are expressly recited in that claim.Rather, inventive aspects lie in a combination of fewer than allfeatures of any single foregoing disclosed embodiment.

Although described in the illustrative context of certain preferredembodiments and examples, it will be understood by those skilled in theart that the disclosure extends beyond the specifically describedembodiments to other alternative embodiments and/or uses and obviousmodifications and equivalents.

1. A fluid turbine system, comprising: a turbine comprising bladesrotatable about an axis, each of the blades comprising a generallystraight front surface portion spaced from the axis, a hook portionextending outwardly from the straight front surface portion, a curvedrear surface portion that is rearward of and curved relative to thestraight front surface portion, and a window that occupies a substantialportion of a height of the blades and is positioned closer to the axisthan the straight front surface portion, wherein a first plane parallelwith and intersecting the axis divides the space surrounding the turbineinto a return side and a push side opposite the return side, the turbineconfigured to rotate generally in an upstream direction on the returnside and generally in a downstream direction on the push side relativeto a fluid flowing nominally parallel to the plane; and a concentratorpositionable in a concentrator position upstream of at least a portionof the turbine and at least partially or completely on the return side,the concentrator having the shape of a leading end of an airfoil or aparabola and comprising a first curved surface portion configured toextend from a first position upstream of the turbine to a secondposition further upstream of the turbine and further into the returnside, wherein the first curved surface portion is configured to beconvex facing an upstream direction of the fluid flow; wherein the firstcurved surface portion deflects at least some fluid toward the push sideand creates a relative vacuum to draw at least some fluid away from thewindow of the blades in the concentrator position, the concentratormovable toward a blocking position further toward the push half relativeto the concentrator position such that the concentrator blocks somefluid from reaching the push half of the turbine.
 2. The fluid turbinesystem of claim 1, wherein the concentrator comprises a second surfaceportion positionable further into the return side relative to the firstcurved surface portion, the second surface portion configured to extendfrom a third position to a fourth position that is further into thereturn side and further downstream than the third position.
 3. The fluidturbine system of claim 2, wherein the concentrator comprises a backsurface portion configured to be concave facing downstream, the backsurface portion comprising an upstream flow surface portion, anintermediate surface portion, and a downstream flow surface portion, theupstream flow surface portion shaped and positionable to direct at leastsome fluid flowing upstream from the turbine toward the intermediatesurface portion, the intermediate surface portion shaped andpositionable to redirect the at least some fluid flowing upstream toflow generally downstream toward the downstream flow surface portion,and the downstream flow surface portion shaped and positionable toreceive the at least some fluid from the intermediate surface portionand direct the at least some fluid generally downstream into the fluidflowing nominally parallel to the plane.
 4. The fluid turbine system ofclaim 2, wherein the concentrator is configured to extend in a directionfurther into the return side at least to an outer edge of the turbinesuch that the concentrator at least intersects a second plane, thesecond plane being tangent to an outermost edge of the turbine andparallel to the first plane.
 5. The fluid turbine system of claim 4,wherein the second plane is separated from the first plane by a bladetip radius, and wherein the concentrator is configured to extend pastthe second plane at least twenty-five percent of the blade tip radius.6. A fluid turbine system, comprising: a turbine comprising a bladeassembly, the blade assembly comprising a plurality of blades rotatableabout an axis, each one of the blades comprising a generally straightfront surface portion spaced from the axis, a hook portion extendingoutwardly from the straight front surface portion, a curved rear surfaceportion that is rearward of and curved relative to the straight frontsurface portion, and an open section closer to the axis than thestraight front portion of the blade, the turbine comprising a push halfand a return half for a given direction of an overall flow of a fluidthat defines an upstream direction and a downstream direction; aconcentrator positionable in a concentrator position directly upstreamof at least a portion of the return half of the turbine, wherein theconcentrator has a shape of a leading end of an airfoil or a parabolaand defines a convex surface facing upstream and a concave surfacefacing downstream when in the concentrator position, wherein when theconcentrator is in the concentrator position, the convex surfacedeflects at least some fluid toward the push half of the turbine, theconcave surface redirects at least some fluid flowing generally upstreamfrom the return half of the turbine to flow generally downstream, theconcentrator movable toward a blocking position further toward the pushhalf relative to the concentrator position such that the concentratorblocks some fluid from reaching the push half of the turbine; and avariable concentrator having a forward end and a rearward end, thevariable concentrator having an airfoil shape and positioned such thatthe rearward end is upstream of the turbine, the variable concentratorlocated on the push half of the turbine, the variable concentratorcomprising a deflection surface extending between the forward end andthe rearward end and operable to deflect fluid, the deflection surfacepositionable to extend generally parallel to the axis along asubstantial portion of a height of the turbine, wherein the variableconcentrator is moveable, in response to a speed of the overall flow offluid, between a first position at lower fluid speeds and a secondposition at higher fluid speeds, and wherein the variable concentratoris configured to deflect more fluid toward the blade assembly in thefirst position than in the second position.
 7. The fluid turbine systemof claim 6, wherein the plurality of blades define a sweep path, andwherein an edge of the sweep path furthest from the push half defines anouter return half edge, and wherein at least a portion of theconcentrator is configured to extend past the outer return half edge ofthe sweep path measured in a direction perpendicular to the overall flowand away from the push half, and wherein the concentrator is shaped andconfigured to draw a drag portion of fluid upstream away from the sweeppath and redirect the drag portion of fluid to flow downstream.
 8. Thefluid turbine system of claim 6, wherein the plurality of bladescomprises four blades, the four blades extendable from the axis, each ofthe four blades comprising a tip and each of the four blades beingpositionable in a lift position, a push position, a catch position, anda return position; wherein the lift position is defined by a bladepositioned such that the tip of the blade in the lift position islocated generally upstream of the axis and the curved rear surfaceportion of the blade in the lift position is convex facing away from thereturn half of the turbine; wherein the push position is defined by ablade positioned such that the tip of the blade in the push position islocated on the push half of the turbine and the straight front surfaceportion of the blade in the push position faces generally upstream;wherein the catch position is defined by a blade positioned such thatthe tip of the blade in the catch position is located generallydownstream of the axis and a front catch surface portion of the hookportion of the blade in the catch position faces generally upstream;wherein the return position is defined by a blade positioned such thatthe tip of the blade in the return position, is located on the returnhalf of the turbine and the curved rear surface portion of the blade inthe return surface position faces generally upstream.
 9. The fluidturbine system of claim 8, wherein the turbine is positionable in atorque position in which a first of the four blades is in the liftposition, a second of the four blades is in the push position, a thirdof the four blades is in the catch position, and a fourth of the fourblades is in the return position, the concentrator and the four bladesadapted to provide favorable torque characteristics in response to theoverall flow of the fluid; wherein the first blade is configured toaccelerate at least some fluid flowing across the curved rear surfaceportion, thereby providing torque; wherein the second blade isconfigured to provide torque by at least some fluid impinging upon thestraight front surface portion; wherein the third blade is configured toprovide torque by at least some fluid impinging upon the front catchsurface portion of the hook portion; and wherein the concentrator isconfigured to reduce drag on the fourth blade by blocking at least somefluid from impinging upon the return curved rear surface portion. 10.The fluid turbine system of claim 9, wherein the plurality of bladesdefine a sweep path, and wherein an edge of the sweep path furthest fromthe push half defines an outer return half edge, and wherein at least aportion of the concentrator is configured to extend past the outerreturn half edge of the sweep path measured in a direction perpendicularto the overall flow and away from the push half.
 11. The fluid turbinesystem of claim 9, wherein the first blade, the second blade, and thethird blade are configured to provide torque simultaneously when theturbine is stationary in the torque position, the open section of thesecond blade located such that at least some fluid passes through theopen section of the second blade and impinges upon the catch surfaceportion of the hook portion of the third blade.
 12. The fluid turbinesystem of claim 6, wherein the open section defined by each of theblades is the same size and shape as the open section of the otherblades.
 13. The fluid turbine system of claim 6, wherein the variableconcentrator is configured to be biased toward the first position. 14.The fluid turbine system of claim 13, wherein the variable concentratoris configured such that the flow of fluid is operable to adjust thevariable concentrator from the first position toward the secondposition.
 15. The fluid turbine system of claim 6, wherein the variableconcentrator is configured to deflect at least some fluid toward theblade assembly when in the second position.
 16. The fluid turbine systemof claim 6, wherein the concentrator and variable concentrator aremoveable around an outer perimeter of the turbine, the fluid turbinesystem further comprising a tail fin adapted to be coupled to theconcentrator and variable concentrator, the tail fin shaped andconfigured to position the concentrator and variable concentratorgenerally upstream of the turbine.
 17. The fluid turbine system of claim16, further comprising a guide motor adapted to be coupled to theconcentrator and variable concentrator, the guide motor configured toselectively control a position of the concentrator and variableconcentrator.
 18. The fluid turbine system of claim 6, wherein theconcentrator and variable concentrator are moveable around an outerperimeter of the turbine, the fluid turbine system further comprising aguide motor adapted to be coupled to the concentrator and variableconcentrator, the guide motor operable to position the concentrator andvariable concentrator upstream of the turbine.